Plasma cutting and plasma arc welding tools are typically powered with a switching power supply. Conventionally, these switching power supplies were configured to have a single fixed switching frequency. The switching frequency was often selected such that the power supply exhibited minimal switching losses at full output current. However, this often resulted in an inefficient supply of power at all except maximum output current. Some modern switching power supplies that are used to power plasma cutters and plasma arc welders may be configured to have two switching frequencies. For example, one frequency may be used for the high current output range and another for the low current output range. However, even with multiple switching frequencies, it may be difficult to maintain proper arc stability with acceptable switching losses throughout the entire operating range of the power supply. In particular, at low output currents, the power supply may have too high switching losses to maintain proper arc stability and at high output currents the current ripple may be greater than desired.
In view of the forgoing, it is apparent that conventional power supplies for plasma cutters and plasma arc welders suffer from the inability to maintain proper arc stability at low currents and experience too high current ripple at higher currents.